Stage controlled air conditioning system



Jlme 27, 1944.- A; B. lNl-:w'roN STAGE cNTRoLLED'AIR coNDIjrIoNING SYSTEM Filed April 30. 1942 INVENTOR Al. ML Atorney Patented 'Junei`27, 1944 STAGE CONTROLLED AIR CONDITIONINGl l SYSTEM'.

Alwin B. Newton, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application April 3o, 1942, serial. No. 441,125

(ci. vcfati 12 Claims.

The present invention relates to air conditioning systems and particularly to control of air conditioning systems wherein both artificial refrigeration and supply of water such as city water is used for cooling.

The primary object of the invention is to provide control means whereby a source of cooling water such as city water, and artiiicial refrigeration may both be used for cooling and dehumidifying in a most efficient and effective manner.

Another object of the invention is to provide percentage of sensible heat removed.

Another object is to provide control means in a system embodying a cooling-coil utilizing city water whereby operation of the said coil is normally prevented when the temperature of the city water supply is not low enough to provide for eiective cooling.

Numerous other objects and advantages of my invention will be apparent from the following detailed description when consideredin the light of the accompanying drawing in which Figure l is a schematic representation of a system embodying the various features of my invention, and

Figure 2 is a view showing a circuit arrangement.

In Figure l, numeral I designates an air conditioning duct of usual type, the right end of which is connected to the inlet of an air circulating fan Il. The fan ll discharges into a duct I2 which communicates with a4 room or other space slightly different I3 wherein the temperature is to be maintained at a desirable value. Fresh air maybe taken into the duct 4IIl through a fresh air passage I4 and return air from the room or space I3 is communicated to the duct I0 through a duct I5 so that it mixes with the fresh air coming in through the passage I4. As is conventional practice in the air conditioning art, `fresh and return air dampers may be provided so as to manually or automatically control the mixture of fresh and return air. I

Disposed in the duct I0 is an evaporator or recapillary tube 2l.

frigeration coil 20 forming a part of a refrigeration system. The refrigeration system or plant is designated by the numeral 2I, and it comprises the vusual refrigerant compressor and condenser l connected in refrigerant flow relationship. The

evaporator is connected .to the plant so as to have refrigerant supplied thereto through a pipe 22, the outlet of the evaporator being connected to tlie compressor of the system through a suction pipe 23. Interposed in the supply pipe 22 is an expansion valve 24 of a conventional type which is arranged to maintain a predetermined degree of superheat in theoutlet vof the evaporator. The expansion valve 24 has operating mechanism including an expansible vand contractible chamber designated by the numeral 25 which is connected to a thermal bulb 2G by a The thermal bulb is disposed in intimate heat exchange relationship with the outlet conduit 23, and it contains a volatile liquid which vaporizes and develops a pressure in the chamber 25 corresponding to the temperature of the superheated gas in the outlet conduit 23.

vThe operation of the expansion valve 24 is well known in the art and need'not be described in further detail. Disposed in the duct I0 ahead of the coil 2|] is another coil 30 which is arranged to have city water or water from another suitable source supplied thereto for cooling purposes.-

Water is supplied to the coil through a pipe 3l and the water is discharged through another pipe, not shown.

The supply of refrigerant to the coil 2D and the supply of water to the coil 30 may be started and stopped by means of an automatic electric valve. Disposed in the supply conduit 22 of the coil 20 is an electric type stop valve 33 which permits normal operation of the evaporator or coil 2liv when it is opened and shuts off the supply of refrigerant when it is closed. Disposed in the pipe 3l is a similar type electric stop valve 34 which permits the flow of water through the pipe 3l when it is open and shuts oi the flow when it is closed. Numeral 35 designates a small by-pass tube which by-passes the valve 34 for a purpose which will presently appear.

The controls for the system include a thermostat responsive to the temperature in the room or space being conditioned. The thermostat 40 includes an expansible and contractible bellows 4I, the movable end of which carries an operating stem which normally engages a pivoted switch `carrying lever 42. Lever 42 carries a mercury switch 43 and the lever is normally biased in a clockwise direction by a coil spring 44. The

mercury switch 43 is of a type having a plurality l of electrodes designated by the numerals 44, 45,

46 and. 41, the electrodes being spaced apart and being spaced from the left end of the mercury tube. When the temperature in the space is relatively low the switch is in the position shown on the drawing with the mercury at the right end of the tube. Upon rising temperatures the lever 42 is tilted in a counter-clockwisee direction as the bellows 4| expands causing the mercury to tend to move towards the left end of the tube. The globule of mercury normally engages electrode 41 and as the tube is tilted in a counterclockwise direction, the mercury will irst engage electrode 46 and this may occur at a temperature of 76, for example. Upon a continued increase in temperature the tube 43 will be rotated in a counter-clockwise direction causing the mercury to successively engage electrodes 45 and 44 at temperatures of 78 and 80, for example. At a temperature of 80, all of the electrodes will be bridged by the mercury. Upon falling temperatures, the electrodes are disengaged by the mercury in a reverse manner.

The thermostat 40 controls a relay 50 com- CTI prising a winding having an armature associated therewith which is attached to a movable switch blade 52 which normally engages a ilxed contact 53 when the relay is deenergized, and which is moved to the right away from the said contact when the relay is energized.

Numeral 55 designates a thermostat or thermostatic controller comprising an expansible and contractible bellows 56 connected to a thermal bulb 51 by a capillary tube 58. 'Ihe thermal bulb 51 is disposed in intimate heat exchange relationship with the pipe 3| or some other frequelntly used pipe through which city water passes or other water which is used for cooling in the coil 30. The bulb 51 contains a volatile liquid which vaporizes and develops a pressure in bellows 56 dependent upon the temperature of the water in pipe 3|. The movable end of the bellows 56 carries a stem which normally engages a pivoted switch carrying lever 59, which carries a mercury switch 50. The lever 59 is normally biased in a counter-clockwise direction by a coil spring 6|. Whenever the temperature of the water in pipe 3| is below a predetermined value, the mercury switch 60 is closed and the switch 60 is opened when the temperature in the pipe 3| rises above a predetermined value which would be too high for effective cooling in the coil 30.

The operation of the system will nowbe explained. With the parts in the position shown, the temperature in the space is below the desired value so that neither of the coils or 20 are-in operation. As the temperature in the space rises in a manner already described above, mercury switch 43 will be moved to a position wherein the mercury bridges electrodes 43 and 41. When this occurs the water coil 30 will be put into operation by means of a circuit causing opening of valve 34, this circuit being as follows: from wire 65, to electrode 41 of mercury switch 43, electrodes 46, wire 56, contact 53, switch blade 52, wire 61, mercury switch 50, wire 68, wire 69, valve 34, wire 10. wire 1| back to wire 12, the wires 65 and 12 being connected to any suitable source of power, not shown. (If the temperature of the water in pipe 3| should be highenough to have mercury switch 63 open, of course valve 34 would not be opened because the water would not then be at a temperature suitably low for cooling in coil 30. The purpose of the bypass 35 is to conduct a very small iiow of water through the coil 33 at all times so that this water will be passed in heat exchange relationship with the bulb 51 so that it at all times measures the temperature of the water and controls the mercury switch 6U accordingly.) Assuming that the cooling load is vincreasing the capacity of coil 33 will not be sufllcient to maintain the temperature desired in the space, and the temperature will continue to rise until the mercury in mercury switch 43 engages electrode 45. When this occurs, relay 50 is energized and valve 33 is opened. 'Ihe circuit for energizing relay 5I is as follows: from wire 65 through electrodes 41 and of mercury switch 43, wire 13, wire 14, winding 5|, wire 15, wire 1|, back to wire 12. When relay is energized, switch blade 52 moves away from contact 53 interrupting the circuit of valve 34 and closing this valve. The circuit for valve 33 is as follows: from wire 35 through electrodes 41 and 45 of mercury switch 43, wire 13, wire 13, valve 33, wire 11. back to wire 12. When valve 33 is thus opened, the refrigerating plant is placed in operation inasmuch as refrigerant is permitted to ilow to the evaporator 23 through pipe 22. The resulting rise in pressure in the evaporator 20 puts the compressor of the refrigerating plant in operation, it being understood that the compressor is controlled in the conventional manner, that is by means of a suction pressure responsive controller. 'I'he evaporator coil 23 will now be operating alone to en'ect both cooling and dehumidiiication of the air in the duct I3, the water coil 30 not now being in operation. The water coil 30 is rendered inoperative at this time so that the refrigeration coil 23 willlremove the desired percentage of latent heat. If the water coil were also operating only a very small percentage of latent heat would be removed by the coil 20. Normally the cooling capacity of the coil 20 will be somewhat greater than that of the coil 33 but assuming that the cooling load is still increasing it will not be suilicient to maintain the temperature in the space alone. Therefore the temperature will continue to rise until the mercury in mercury switch 43 engages electrode 44, this closing another circuit causing 34, this circuit being as follows: from/wire through electrodes 41 and 44 o'f""rrcury switch 43, wire 13, wire 33, valve 34, wire 10, wire 1|, back to wire 12. Valve 34 now opens for supplying water through the coil 30 so that both of the coils are operating, their combined capacityproducing maximum cooling of the air passing through the duct I3.

It will be noted that the circuit for valve 34 is now independent of the thermostatic controller 55 sol that the valve will now be opened'irrespecopening of the valve tive of the temperature of the water entering through pipe 3|. When both of the coils are operating even if the water temperature is relatively high, it will be low enough to have some cooling eilect on the air before the air passes over the refrigeration coil 20 and thus the e!- fectiveness of the system will be increased by that much.

`Upon falling temperatures, the sequence oi' operation is the reverse of that described above,- that is first the water coil 30 will be cut oi! while coil 20 operates alone, then operation o! the refrigeration coil 20 will be discontinued while the coil 30 is turned on again, and finally the coil 30will be turned ofi.

My arrangement provides a way of utilizing the water supply andthe artillcialrefrigeration to the best advantage whereby the. system is operated to produce cooling under the most effective and eillcient conditions; Economy is promoted by operating the water coil only when its cooling eii'ect can be eiectively utilized and the load is not such as to require use of the artificial refrigeration. By operating the refrigeration coil alone under moderate load conditions, the proper ratio is maintained between sensible cooling and the'removal of latent heat. .Under maximum cooling load the water coil is rendered operative so that the system will perform a maximum amount of sensible cooling while lowering ,the ratio of latent to sensible cooling. In other words, under maximum cooling loads the system is operated to remove a maximum amount of sensible heat at the expense of the humidity of the air passing `over the coils. As soon as the temperature in the space is reduced the water given the same reference numerals as in Figure 1. The thermostatic switch 55 is also adapted to respond to the temperature of the source of supply of the cooling water in the same manner as in connection with the system disclosed in Figure 1. In Figure 2, however,a slightly different form of thermostatic switching arrangement for the space is used. 'I'his thermostatic switching mechanism comprises a temperature responsive bellows which actuates three separate mercury switches indicated at |0|, |02, and |03. The mercury switch |02 is illustrated as a doubleended switch and it is so arranged that as the switch is rotated in a counter-clockwise direction upon expansion of the bellows |00, the mercury will rst unbridge the` electrodes |04 and |05 and then upon a slight increase in temperature will bridge the electrodes |06 and |01, the electrodes and |06 being connected electrically to the common conductor |00, and thus forming together the common electrode of the switch.V

The bellows |00` is shown in the position in which it will occupy when the temperature in the space is such that no cooling is required. Under these circumstances, the mercury switches |0i and |03 `will be in open circuit position and the mercury in the mercury switch |02 will be bridging the two electrodes |04 and |00 in the right hand end of the switch. When the tem- I perature in the space to beconditioned increases slightly indicating a very light load, the bellows |00 will expand and cause all of the mercury switches to be rotated in a counter-clockwise direction. At a temperature of 76, for example, the bellows |00will expand far enough tocause the mercury in the switch |0| to move to the left hand end of the switch and establish a circuit whch extends from the line wire ||0 through conductors and |00, electrodes |05 and |04, conductor ductor ||3, thermostatic switch 55, which will be closed if the water temperature feeding the coil 30 is sufll'ciently cool, conductors |4 and H5, solenoid valve 34 controlling the supply of cooling water to the coil 30 and conductor I I6 to the other line wire ||1. The'establishment of this circuit therefore provides for the flow ofv water to the water coil 30 and the subsequent cooling oi the air passing through the conditioning ||2, mercury switch |0|, conchamber I0. If the load on the system continues to be very light the temperature of the air in the space to be conditioned will decrease and-the bellows |00 will accordingly contract and open the above circuit. The temperature in the space will therefore be maintained at approximately 76 in the above manner under light loads.

If the load on the system increases the bellows solenoid valve 34 at which time the water coil will no longer cool the air passing through the conditioning chamber I0.

At this time the temperature in the space will probably continue to increase due to the deenergization of the water coil 30 and after an increase of about a quarter or half a degree in temperature the bellows |00 will have expanded far enough to cause the mercury in the mercury switch |02 to bridge the electrodes |06 and |01. This will establish a circuit from the line wire ||0 through conductors and |08, electrodes |06 and |01, conductor H9, solenoid valve 33 for the refrigeration coil 20, and conductor |20 back to the other line wire This will result in the energization of the refrigeration coil 20 which will be in operation alone and which will, as described above, maintain the proper ratio between I latent and sensible cooling.` I f the capacity of the refrigeration coil 20 alone is sufficient to de-V crease the temperature in the space then thc refrigeration coil 20 will be deenergized by the mercury switch |02 without the reenergization of the water coil 30. In other words, the mercury switch |02 will be rotated in a clockwise direction far enough tov unbridge `the electrodes |06 and |01 but not far -enough to bridge the elecltrodes |04 and |05. If the temperaturethen increases in the space .the mercury switch |02 will then again energize the refrigerationcoil 20. Therefore, under moderate loadconditions the vtemperature within the'space will be maintained by the alternate Venergization and delenergization of the refrigeration coil 20 without the operation of the water coil 30.4 that the mercury switch |0| controls the solenoid valve 34 ,at a differential of from 1 to 11/2" and that the mercury switch |02 controls the solenoid valve 33 at a-diierential of from l to l1/2" and that there is approximately a half a degree differential between the operation of the two solenoid valves 33 and 34,

If the cooling load on the system should be so heavy that the refrigeration coil 20 is incapable of maintaining the temperature in the space below 80. then the bellows |00 will expand sufficiently t0 cause the mercury switch |03 to move to closed circuit position. This will establish a circuit from the line wire |0 through conductors |2|, mercury switch |03, conductors |22 and H5, solenoid valve 34 and conductor` ||6 back to the other line wire |1. Thus, when the temperature in the space reaches'80 both the rel frigeration coil 20 and the water coil 30 will be rendered operative to effect the maxmium amount of sensible cooling. Of cour-e if the temperature in the space should then be lowered to a value somewhat below 80"`v the mercury switch |03 would again move to open circuit posi.v

It might be pointed out tion and deenergize the solenoid valve Il for the water coil 30.

If desired the usual two-position type of mercury switch may be substituted for the mercury switch |02 so that as soon as the mercury unbridges the electrodes |04 and |06 it will bridge the electrodes |08 and |01. Ifsuch a switch is used it will be obvious that the sequence of operation of the water coil and the refrigeration coil will be exactly the same as that described in connection with the modiiloation shown in Figure 1. As many other changes and modifications oi this system may occur to those who are skilled in the art, I desire it to be understood that I intend to be limited only by the scope of the appended claims and not by the specific embodiments oi' the invention which have been disclosed herein for the purposes of illustration.

I claim as my invention:

1. In an air conditioning system, in combination, air cooling means comprising artiilcial refrigerating means, means comprising a heat exchanger having a source of iiuid supply therefor, and means responsive to cooling requirements i'or first operating the heat exchangerv alone, then operating the artificial cooling means alone, and then operating both the heat exchanger and the articlal cooling means in response to increasing cooling requirements.

2. In an air conditioning system, in combination, air cooling means comprising artificial refrigerating means, means comprising a heat exchanger having a source of water supply therefor, means responsive to cooling requirements for first operating the heat exchanger alone, then operating the artificial cooling means alone, and then operating both the heat exchanger and the artiilcial cooling means in response to increasing cooling requirements, and means for preventing operation of the heat exchanger when the temperature oi' the -supply water is above a predetermined value.

3. In an air conditioning system, in combination, air cooling `means comprising articial refrigerating means, means comprising a heat exchanger having a source of water vsupply therefor, means responsive to cooling requirements for iirst operating the heat exchanger alone, then operating the articial cooling means alone, and

then operating both the heat exchanger and the artiiicial cooling means in response to increasing cooling requirements, and means responsive to the temperature of the water supplied to the heat exchanger for preventing supply of water thereto when the temperature of the water is above a predetermined value upon a demand for operation oi' the heat exchanger alone.

4. In an air conditioning system, in combination, air cooling means comprising artificial refrigerating means, means comprising a heat exchanger having a source of water supply therefo'r, means responsive to cooling requirements for first operating the heat exchanger alone, then operating the articial cooling means alone, and then operating both the heat exchanger and the 'artificial cooling means in response to increasing cooling requirements, and means responsive to the temperature of the watersuppiied to the heat exchanger for normally preventing the water from being supplied thereto when the temperature of the water is above a predetermined value, the said means responsive to cooling requirements having means for causing both the heat exchanger and the articial refrigerating means to operate y ther increased irrespective oi said temperature responsive means under heavy cooling load requirements.

5. In apparatus of the character described. in combination, air cooling means comprising a water coil and a refrigeration coil, means responsive to cooling demands for operating the water coil upon a demand for cooling. said cooling demand responsive means embodying means for turning oil the water coil and turning on the refrigeration coil upon increased cooling demands and for again turning on the water coil upon furcooling demands.

6. In apparatus of the character described, in combination, a heat exchanger adapted to have .water circulated therethrough. a rei'rigerating system having an evaporator, means i'or passing air over said heat exchanger and evaporator, a valve controlling the flow oi' water to the heat exchanger, a second valve controlling the now oi refrigerant to the evaporator, control means comprising a multi-stage thermostat responsive to the temperature of the air, means whereby upon an initial rise in temperature the thermostat opens the nrst valve admitting water to the heat exchanger, means whereby upon aviurther rise in temperature the thermostat closes the nrst valve and opens the second valve, and means whereby upon a still further rise in temperature the iirst valve is reopened.

7. In apparatus oi' the character described, in combination, a heat exchanger adapted to have Vwater circulated therethrough, a retrigerating system having an evaporator, means for passing air over said heat exchanger and evaporator, a valve controlling the ilow of water to the heat exchanger. a second valve controlling the now oi' refrigerant to theevaporator, control means comprising a thermostatic means responsive to temperature of water flowing tothe heat exchanger and a multi-stage thermostat responsive to the temperature oi' the air, means whereby upon an initial rise in temperature the thermostat opens the iirst valve dependently on said thermostatic means for admitting water tothe heat exchanger,

" means whereby upon a further rise in temperature the thermostat closes the first valve and opens the second valve, and means whereby upon a still further rise in temperature. the thermostat reopens the ilrst valve irrespective oi' said temperature responsive means.

8. In an air conditioning system comprising in combination, a first heat exchanger for removing principally sensible heat from the air to be conditioned, a second heat `exchanger for removing substantial amounts oi' both sensible and latent heat from the air to be conditioned, and means responsive to the temperature oi' the conditioned air for rendering said rst heat exchanger operative when thetemperature is such as to in- 6o dicate a relatively light load on the system, for

combination. a ilrst heat said rst heat exchanger wendering said iirst heat exchanger inoperative and said' second heat exchanger operative upon an increase in said load. and for rendering both oi said heat exchangers operative upon a still further increase in said load.

9. In an airconditioning system comprising in exchanger for removing principally sensi-ble heat from the air to be conditioned, a second heat exchanger for removing substantial amounts of both sensible and latent heat from the air to be conditioned. means rendering operative when the temperature of the conditioned air is within a first predetermined range. rendering both of said heat exchangers inoperative when said temperature is v within astill higher range,

within a higher range. rendering said second heat exchanger operative when said temperature is and rendering both of said heat exchangers operative when said temperature' exceeds said last named range.

10. air conditioning system comprising in combination, a iirst heat exchanger for removing priii'cipally sensible heat from the air to be conditioned, a second heat exchanger for removing substantial amounts of both sensible and latent heat from the air-to be conditioned, a thermostat res ive to the temperature of the condivl', a iirst switch operated by said thermostat upn an increase in temperature for rendering saidf'rst heat exchanger operative, a second switchpperated by said thermostat at a higher temperature for rendering said first heat exchanger` inoperative and said second heat exchanger?a operative, and a third switch operated by said? thermostat at a still higher temperature torendering said rst heat exchanger operative again.

11. 'L' 'an air conditioning system comprising in combination, a nrst heat 'exchanger for removing principlly sensible heat from the air to be condition a second heat exchanger for removing substantial amounts of both sensible and latent heat from the air to be conditioned, a thermo-I stat responsive to the temperature oi the conditionedlair, a nrst switch operated by said thermon said thermostat at a stili ing said iirst heat exchanger operative, a second switch operated by said thermostat at a highertemperature for rendering said rst heat exchanger inoperative and said second heat exchanger operative, and a third switch operated by higher temperature for rendering said iirst heat exchanger operative again, said second switch rendering said second heat exchanger operative at a higher temperature than that `at which it renders said first heat exchanger inoperative.

12. In an air conditioning system comprising in combination, air conditioning means comprising artificial refrigerating means and heat exchanger means having a source of cooling iluid therefor, a temperature responsive device, meansoperated yby said device for controlling heat exchanger means to maintain the proper temperature when said temperature is within a first predetermined range, said controlling means rendering said heat exchange means inoperative when said temperature is within a relatively small higher range. means operated by said device for controlling said articial refrigerating means to regulate the temperature when said temperature is within a still higher range. and means operated by said device to reenergize said heat exchanger means when the temperature exceeds said last named range.

' ALWIN B. NEWTON. 

